1. Field of the invention
This invention relates to a device implantable in the living body for attachment and augmentation of tendons and/or reinforcements of bones.
The device according to the invention is particularly useful for the attachment and augmentation of the disrupted tendons of the rotator cuffs and the reinforcement of the proximal humeral bone.
Disorders of the rotator cuff are the most common cause of painful shoulder disability. The natural history of untreated ruptures of the rotator cuff are much less favourable than previously thought. Attempts of surgical repair of ruptures almost consistently yield satisfactory pain relief, in contrast to functional restoration which is less certain, particularly in large tears. This has been attributed to a variety of factors:
the quality of muscle motoring the tendon may be irrevocably poor; PA1 the quality of the tendon (circulation, elasticity, tensile strength) may preclude repair; PA1 the quality of cancellous bone may not provide enough stability (e.g. in the case of osteoporosis); or PA1 the patient's lack of cooperation may defeat the surgical goal.
It has been established, that functional restoration of the shoulder does not depend on the cuff rotator tear size, but on the success of repair of the defect. Thus the anatomical and mechanical success of operative tendon-to-bone attachment is therefore of great importance.
Several factors, which influence the quality of repair such as the suture material, the quality of initial fixation, the tension in the musculotendinous unit and the load applied during the postoperative course influence the success of the repair. One of the important problems is how to grasp the tendon with the suture material to achieve a strong and secure attachment of the tendon to the bone.
2. Description of the Prior Art
Very few literature data concerning this problem are available and yet refer to the surgical attachment of the supraspinatus tendon, e.g. as described in an article of France, Paulos, Harner and Straight "Biomechanical evaluation of rotator cuff fixation methods" published in Am J Sports Med 17:176-181,1989.
Different prior art methods of soft tissue-to-bone fixation have been evaluated, e.g. fixation to bone by spiked washers and screws, using spiked soft tissue plates, different kinds of staples and suturing. It has been found that independently on the suturing technique used, the suture material pulls through the tendon.
It has been also observed that when using prior art non-augmented techniques for the tendon-to-bone attachment [e.g. according to the Kessler technique described in ML Mason, HS Allen, "The rate of healing of tendons An . experimental study of tensile strength", Ann Surg 113-3, 424-59(1941);
AD Forward, J Cowan, "Tendon suture to bone", J Bone Joint Surg 45-A(4), 807-823(1963); and
LD Ketchum, NL Martin, DA Kappel, "Experimental evaluation of factors affecting the strength of tendon repairs", Plast Reconstr Surg 59(5), 708-719(1977)] there is a diastasis formed between connected elements, while suture applied to the tendon strangulates and/or pulls out the tendinous tissue.
Attempts have been made (France, Paulos, Harner and Straight "Biomechanical evaluation of rotator cuff fixation methods" published in Am J Sports Med 17:176-181,1989) to strengthen tendon-suture interface by interposing a polytetrafluoroethylene (PTFE) membrane between suture and tendon. Although it was expected that the membrane will augment the holding power of the tendon, no significant improvement was observed.
In addition it was observed in reoperations that shoulder function is usually not achieved, because of diastasis between the tendon and bone. While the suture material stays always intact, the tendon is connected to the bone through functionally insufficient scar tissue.